The present invention is directed to a biodegradable surface for sports and other uses and, more particularly, to a combination of artificial and natural surfaces supported by a biodegradable backing.
For years natural turf surfaces were used for most outdoor sports, for example, soccer, football, field hockey, cricket, rugby, etc. Natural turf surfaces are surfaces constructed with a grass grown in soil, or some other surface layer of growth medium (e.g., sand and organic mixes, etc.), that is constructed upon a suitable foundation. A natural turf surface is generally preferred for its comfort, feel, grip, and appearance.
However, under heavy use and/or poor weather conditions, natural turf surfaces deteriorate rapidly and maintenance is costly. Intense activity on the turf destroys the grass and its root system, leaving mud and/or dirt on the playing surface. Prior to re-establishment of the turf, the surface is unsightly and often pockmarked, uneven, and possibly hazardous to use.
Another problem associated with natural turf surfaces is the use of painted-on yardage and boundary lines. Typically, such boundary lines are formed by painting the playing surface. For aesthetic reasons, such lines are generally painted just prior to each official game played on the playing surface. The repeated application of paint to the surface of the playing surface tends to kill the grass that is located under the painted surface. In addition, over time the multiple layers of paint build up, forming a surface that is substantially harder than the surrounding natural grass playing surface. Thus, the painted areas of the playing surface can create slippery spots within the playing surface, possibly leading to slips and falls by athletes using the playing surface. In addition, the painted areas can increase the possibility of injury to the athlete and create hard spots that can be uncomfortable or painful to an athlete who falls upon the painted area.
Due to the needs of sports programs, even after destruction of portions of the turf, play usually continues on the playing surface, even when the surface is badly damaged, until the sport""s season is over, when the turf can be reestablished. Thus, the playing conditions on the playing surface continually decline over the season. At the end of the season, the natural turf surfaces are reseeded, the divots leveled and filled, etc. The natural turf surfaces are not usable during this reestablishment period because use defeats the reestablishment of the turf. The reestablishment period typically takes at least four months, or longer, under ideal weather conditions, during which the natural turf surface should not be used.
Recently, synthetic surfaces have been used as an alternative to natural turf surfaces. Synthetic surfaces generally come in two types, i.e., conventional and sand filled. Conventional synthetic is a dense synthetic material that has the appearance of dense grass blades. Sand-filled synthetic is a synthetic material similar to conventional synthetic turf, but with greater spacing between the blades, to accommodate a silica sand filling.
Both the conventional and sand-filled synthetics are placed indoors or outdoors, upon a foundation that may include an asphalt, concrete, wood, or other supporting subsurface along with cushioning mats, water drainage, and water irrigation.
Although synthetic turf surfaces are more durable than well-established natural turf surfaces, they are only moderately successful for sports and other uses. The most notable disadvantages of synthetic turf surfaces are the discomfort for the players and an increased number of injuries. Additionally, synthetic turf surfaces are generally expensive to put in place and have a life expectancy of 8 to 15 years, if properly maintained, and less if poorly maintained. Outdoor synthetic turf surfaces also remove large areas from the ecosystem, reducing natural processes including ground water recharge, oxygen and carbon monoxide balance, temperature modulation, and dust filtration. For these and other reasons, a number of synthetic turf surfaces are currently being converted back to natural turf surfaces.
As can be seen from the above discussion, there exists a need for an improved surface for sports and other uses, and a method of making the improved surface, wherein the surface provides improved comfort and fewer injuries to the users, while being durable under heavy use and in poor weather conditions. The present invention is directed to fulfilling this need.
The present invention provides an improved surface for sports fields and for other high-traffic uses. In one embodiment, the surface includes a foundation and a synthetic turf base that is positioned atop the foundation. The synthetic turf base is filled with a layer of growth medium, and includes synthetic fibers mounted in a permeable backing material. The backing includes a plurality of openings to allow water drainage and natural grass root growth therethrough. The synthetic fibers are constructed of a flexible, synthetic material and extend generally vertically upward from the backing material. Natural grass is planted in the growth medium so that the roots grow downward through the growth medium, through the backing material, and into the foundation. The blades of the grass grow upward from the top of the growth medium to form a playing surface.
In accordance with one aspect of the invention, the backing material is formed at least partially of a biodegradable material. In one embodiment, the biodegradable backing may be a woven material partially or completely formed of biodegradable strands. In another embodiment, the backing may be a mesh that is partially or completely formed of biodegradable material. The biodegradable backing degrades over time so as to increase the size and number of the openings through the backing to allow increasing growth of the roots of the natural grass into the foundation.
In accordance with other aspects of the invention, a mesh material is placed between the foundation and the synthetic turf base. The mesh material is located in the region of adjoining edges of the synthetic turf base and underlies the adjoining edges of the synthetic turf base. The roots of the grass plants grow through the synthetic turf base, through the mesh material, and into the foundation, thus binding different pieces of the synthetic turf base to the mesh material and the foundation. The mesh material can include protrusions extending from either one or both sides of the mesh material. The protrusions extend into the foundation and into the backing material in order to help anchor the edges of the synthetic turf base.
According to yet another aspect of the invention, the synthetic fibers are provided in two lengths: a first group of fibers having a first length and a second group of fibers having a second length that is shorter than the first length. The first group of fibers extends upward from the backing material a greater distance than the second group of fibers. A layer of growth medium is disposed in the synthetic turf base to a depth sufficient to substantially fill the synthetic turf base. In various embodiments, the layer of growth medium may be filled to a level that is below, at, or above the top of the first or second group of fibers.
In accordance with other aspects of the invention, the first group of fibers is uniformly interspersed throughout the playing surface. The first group of fibers extends upward and is intertwined with the natural grass blades. The first group of fibers protects the crowns and blades of the natural grass, while the second group of fibers protects the crowns of the grass plants.
In accordance with other features of the invention, the first group of fibers is formed of a color that contrasts with the grass and provides a visual indicator. The first group of fibers is placed in an organized pattern to provide boundary indicators, line indicators, etc. The backing material in the region of the first group of fibers is formed of a material that is root impervious. The backing material may also include an herbicide to prevent natural grass plants from growing into and through the backing material in the region of the first group of fibers.
The playing surface of the present invention improves the durability and visual appearance of natural grass playing surfaces. The playing surface of the invention helps to protect the crowns of the natural grass plants, thus helping to prevent damage to the natural grass. This allows the present invention to produce a playing surface that recovers more quickly than natural grass playing surfaces. At the same time, the playing surface of the present invention is formed substantially of natural grass blades, thus providing the comfort and appearance of a natural grass playing surface.